1. Field of the Invention
The present invention relates to a wafer cleaning apparatus for cleaning wafer, which are processed by various processing steps such as plating and chemical mechanical polishing.
2. Description of the Related Art
When metallic materials such as copper attach themselves to the surfaces and edges of semiconductor wafer electro-chemically as metallic copper, they become stable and cannot be removed by washing with pure water. Copper adhering in such a manner will diffuse into silicon wafer during heat treatment, and causes problems in device performances.
On the other hand, a copper seed layer is currently formed as a pretreatment for copper plating by sputtering copper (or by CVD) on the silicon wafer, and the trend is to apply the layer over the entire front surface of the wafer, because it is a more efficient use of the area. That is, as shown in FIG. 1, a barrier layer 80 is formed on the front surface of the wafer W extending to its edge section E, a Cu seed layer 83 is formed thereon, and a plating layer 85 is formed on the seed layer 83.
However, when a Cu seed layer 83 of 100 nm, for example, is formed by sputtering on the entire front surface of the wafer W, a sputtered Cu layer is formed not only on the front surface of the wafer but a thin sputtered Cu layer is formed also on the edge section E of the wafer as shown in FIG. 2. On the other hand, the formation of the plating layer 85 on the wafer W is carried out by sealing the outer peripheral section of the wafer W so as to prevent the plating layer from extending to the back surface of the wafer W. Therefore, the plating layer 85 can be formed only on the front surface of the wafer W not extending to the edge thereof, as shown in FIG. 2. For this reason, a portion of the Cu seed layer 83 remains on the edge section E and in the vicinity thereof as a thin layer. The residual Cu layer in such places can detach and be removed from the wafer during transport or processing of plated wafers or chemically mechanically polished (CMP) wafers, thereby leading to a high probability of causing Cu crop-contamination.
Also, it is difficult to prevent Cu from adhering to the back surface and edge of the wafer even if the edge and the back surface are protected by sealing the outer periphery thereof.
The present invention has been derived in view of the background problems outlined above, and an object of the present invention is to resolve such current problems and provide a wafer cleaning apparatus for completely cleaning surfaces of wafer processed by copper plating, a CMP process or so on.
The present invention provides an apparatus for cleaning front and back surfaces of a wafer while rotating the wafer that has been subjected to a fabrication process. The apparatus comprises: cleaning nozzles for spraying a cleaning solution, respectively, onto a front surface of the wafer that has been processed and onto a back surface thereof; and an etching nozzle for spraying an etching solution onto a vicinity of an outer periphery of the wafer.
According to cleaning the processed front surface of the wafer, particulate matter and detached copper are eliminated therefrom. According to cleaning the back surface of the wafer, particulate matter and/or copper adsorbed as metallic copper, are eliminated. And according to etching the edge portion of the wafer, it is possible to forcefully eliminate a thin copper film by etching.
As explained above, the present invention enables both sides and edges of the wafer to be cleaned at the same time as well as preventing potential device problems caused by metals, ouch as copper, adhering to the edge section of the wafer. That is, device performance problems caused by contamination from adhered metal on the edge section and back surface of the wafer, and problems of cross contamination caused by detached metal film from the copper formed on the edge section, are prevented. Thus, the invention provides beneficial effects of facilitating ideal cleaning of processed wafer that received various processing such as copper plating and a CMP process that follows the plating process.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.